Rehabilitation of water supply pipes

ABSTRACT

Device for use in rehabilitation of water supply pipes includes a tubular liner (10) which is deployed through a pipe (11) for example by a line attached to a messenger pig which is propelled through the pipe. The liner (10) has a multi-lobed pleated cross-section, and is of a polyolefin elastomer material, e,g, a substantially linear ethylene inter-polymer. The liner is extruded and die drawn during extrusion to produce a reduced diameter highly oriented structure.

FIELD OF THE INVENTION

This invention relates to improvements in the rehabilitation of watersupply pipes.

BACKGROUND OF THE INVENTION

Domestic water supply systems are usually connected to the watercompany's main by a service pipe, in two parts, the water company's pipemaking an end to end junction with the customer's pipe at the highwayboundary. A major public health problem remains the large number ofpremises which are still equipped with lead pipes, as the slightlysoluble lead is a well known cumulative poison. One approach to thisproblem has been to replace lead piping with polyethylene plasticstubing. Alternative ductile metals such as copper have their owncumulative hazards.

As an alternative to replacement of lead pipes, it has been proposed toline the pipes with a polyethylene film which is everted by fluidpressure into the pipe (see WO97/04269) or a polyethyleneterephtalate(PET) film which is extruded as a profile and inflated by fluid pressurewhen heated in situ. This presses the lining against the inner walls ofthe pipe, and softens the lining to achieve a measure of thermal bondingto the pipe wall.

The known techniques all involve significant investment in capital plantand equipment, including those outlined above and also the use of impactmoles (usable in compactable soils but not capable of being steeredaround obstructions such as other utility conduits gas, sewage,electricity, etc . . . ), pipe pulling, pipe splitting, guided drilling,pipe pushing, narrow trenching rods and powerful vacuum excavators.

BRIEF DESCRIPTION OF THE INVENTION

An object of the present invention is to provide a simpler and cheapertrenchless method by which existing lead water pipes, particularlyunderground pipes, can be rehabilitated with the minimum of disruptionto the customer's property and without the need for expensive plant andequipment.

According to the invention, there is provided a method of rehabilitatingwater supply pipes comprising deploying a tubular liner within a pipe,characterized in that the liner comprises a polyolefin elastomer or apolyolefin plastomer. A polyolefin elastomer has a density below 870kg/m³, whereas polyolefin plastomer has a density above 870 kg/m³.

The invention also provides water supply pipes which comprises a tubularliner of a polyolefin elastomer or plastomer and an apparatus for makingwater supply pipe and using the method of rehabilitating water supplypipes.

The polythene elastomer/plastomer preferably comprises a substantiallylinear ethylene interpolymer, which may comprise 50-95% by weight ofethylene, and 5-50% by weight of at least one olefinic co-monomer,preferably 10-25% by weight of the co-monomer. Co-monomers may containfrom 3 to about 20 carbon atoms, and may comprise one or more ofpropylene, 1-butene, 1-hexene, 4-methyl-l-pentene, 1-heptene, and1-octene. The density range may be in the range of 830 to 967 kg/M³,preferably 863 to 913 kg/m³ and more preferably 885 to 913 kg/m³, foroptimum toughness and flexibility. Preferred co-monomers are 1-hexene,and especially 1-octene.

The substantially linear inter-polymers are advantageously characterizedby a narrow molecular weight distribution, especially from 1.8 to 2.2and a homogenous co-monomer distribution.

The tubular liner preferably is formed as a pleated tube formed withlongitudinally extending multiple radial pleats, giving a star shapedmultilobed or fluted cross-section. The tube is preferably formed withsix radially equispaced pleats, defining an equal number of outwardlyprojecting lobes.

The liner may be deployed within a pipe, by securing one end of theliner adjacent an end of the pipe to which access has been obtained, andpulling the liner through the pipe by means of a line which may beattached to a foam messenger pig and propelled through the pipe by fluidpressure. Alternatively the liner may be pushed and pulled through thehost pipe by means of a flexible rod attached to the liner.

The liner is preferably extruded in the pleated tube form from thepolyolefin elastomer/plastomer, and has an outer diameter significantlysmaller than the internal diameter of the pipe to be rehabilitated,

The liner may be die drawn during the extrusion process whilst thematerial is at just below the crystallisation melt temperature of thepolymer, to impart a significant reduction in size of the extrusion ascompared with the die, and also produces significant orientation of thepolymer in the axial direction of the extrusion. This orientation in thedirection of extrusion provides stiffness and resistance to kinking.

BRIEF DESCRIPTION OF THE DRAWINGS

A preferred embodiment of the liner and rehabilitation method accordingto the invention will now be further described by way of example, withreference to the accompanying drawings, wherein

FIG. 1 is an enlarged sectional view of a liner according to theinvention deployed within a domestic water supply pipe

FIG. 2 is a similar enlarged sectional view of the liner of FIG. 1expanded by internal pressure so as to be forced into contact with theinner wall of the pipe;

FIG. 3 is a fragmentary sectional view of the liner as shrunk after diedrawing;

FIG. 4 is a sectional view taken along the axis of the pipe, of a firstterminal arrangement for enclosing an end of the liner duringinstallation;

FIG. 5 is a similar view of a second terminal arrangement for enclosingan end of the liner during installations.

FIG. 6 is a sectional view of the pipe and liner showing the use of aflexible rod.

FIG. 7 is a sectional view of the pipe and liner showing the use of apig and attached leader line.

DETAILED DESCRIPTION OF THE INVENTION

The liner 10 is shown in FIG. 1 inserted axially within a lead waterpipe 11, having an inner wall 12. The liner 10 comprises an extrusion ofa polyolefin elastomer or plastomer, such as a substantially linearethylene inter-polymer, of a kind to be described in more detail below.

The liner 10 has a generally star-shaped or lobed cross-sectional shape,provided by six longitudinally extending pleats 13, and six ribs 14.

The diameter, measured between opposed rib crests is about 8 mm, whichenables the liner to be inserted easily within the bore of a leaddomestic water pipe, which is typically from 10 to 20 mm internaldiameter.

This shape and dimension enables the liner to be deployed axially alongthe pipe, and to negotiate bends in the pipe, without twisting orkinking.

FIG. 2 shows the pipe 11 and liner 10 after inflation of the liner byinternal pressure such as that afforded by water supply pressure, sothat the elastomeric lining expands, and is maintained in contact withthe inner wall 12 of the pipe by the water pressure.

FIGS. 4 and 5 show two embodiments of device for enclosing one end ofthe liner 10 at the accessible end of a pipe 11 during deployment of thelining into the pipe. In FIG. 4, the end of the pipe 11 is received atan abutment in an outer adaptor 20 which is received in the open end ofa coupling 21, and secured about the pipe end by a compression nut 22screwed to the coupling 21 and to the pipe end by a grip ring 23.

An inner adaptor, in the form of a tapered member 24 receives an end ofthe liner 10 and clamps it with a seal ring 25 in cooperation with aninner face of the outer adaptor 20.

The FIG. 5 embodiment has all these features, but differs in that theend of pipe 11 is held by a locking collar 26 to a stub shaft 27 whichis held by the compression nut 23, by means of clips 28.

The liner 10 in the preferred embodiment is a tubular extrusion of apolyolefin elastomer or plastomer. This is produced from a substantiallylinear ethylene inter-polymer such as described in U.S. Pat. No.5,272,236, U.S. Pat. No. 5,278,272, and U.S. Pat. No. 5,380,810. Suchpolymers are supplied, e.g., by DuPont Dow Elastomers S. A.(“substantially linear” means that the bulk polymer has an average of0.01 to 3.0 long chain branches per 1000 carbon atoms, preferably from0.01 to 1.0 long chain branches per 1000 carbon atoms). Polymers withfewer than 0.01 long chain branches per 1000 carbon atoms are describedas “linear”.

The ethylene inter-polymer preferably contains 50-95% by weight ofethylene and 5-50% by weight of at least one alpha-olefin co-monomer,preferably 10-25% by weight of co-monomer. The percentage of co-monomeris measured by infra red according to ASTM D-2238. The alpha-olefin mayhave up to about 20 carbon atoms, for example propylene, 1-butene,1-hexene, 4-methyl-1pentene, 1-heptene and 1-octene are especiallypreferred, more especially 1-octene for use in the liner. The thusproduced inter-polymers are characterized by a narrow molecular weightdistribution and by a homogenous co-monomer distribution. The molecularweight distribution (Mw/Mn) measured by GPC (Gel PermeationChromatography) is defined by the equation Mw/Mn (I₁₀/I₂)−4.63. Thepreferred density range of the interpolymer is from 863 to 913 km/m³because the liner is flexible and yet has an excellent burst strengthdue to tie chain molecules.

One suitable liner material has the following specifications:

Test Physical Properties Co-monomer Content, wt % 9.5 Dow Melt Indexdg/min 1.0 ASTM D-1238 density g/cm³ 0.908 ASTM D-792 Moulded PropertiesUltimate Tensile Strength MPa 33.0 ASTM D-638M-90 Flexural Modulus, 2%Secant MPa 141 ASTM D-790 Ultimate Tensile Elongation % 700 ASTMD-638M-90 Hardness, Shore A/D 96/49 ASTM D-2240 Thermal Properties VicatSoftening Point ° C. 97 ASTM D-1525 DSC Melting Point 103 DuPont/Dow

The polymers are produced using, for example, the INSITE TECHNOLOGY(DuPont Dow Elastomers SA, Registered Trade Mark), a process whichallows control over polymer structure, properties and rheology. Bycontrolling molecular architecture, INSITE (TM) makes possible a verynarrow molecular weight distribution and controlled level ofcrystallinity, leading to key advantages such as control of flexibility,hardness, elasticity, compression set and heat resistance. Theseproperties can be further improved by compounding and the use offillers, and cross-linked using silane, peroxide or UV or otherradiation.

Typical properties of a polyolefin elastomer/plastomer are summarised asfollows:

density (g.cm³), ASTM D-792 0.864-0.913 Flexural Modulus, 2% Secant, 7-190 Mpa, ASTM D-790 100% Modulus, Mpa, ASTM D-412 1 to 5 Elongation,%, ASTM D-638 77+ Melting Point, ° C.  50-100 Hardness, Shore A, ASTMD-1003 10-20 Melt Index, 12, ASTM D-1238, dg/min 0.5-30 Low TemperatureBrittleness, T, ASTM D-746 Below −76

The polymer can be processed in the same way as a thermoplastic andperforms as an elastomer/plastomer.

The liner made from this material takes advantage of the properties ofthe polymer especially elasticity which allows for considerable radialexpansion under pressure, coupled with an increase in the flow rate dueto the excellent processability of the polymer.

The density of the preferred material is in the range of 902 to 908kg/m³, tensile strength from 32-33 Mpg, and ultimate elongation up to800%.

However, the higher density material has been found to perform mostsatisfactory.

The liner 10 is extruded by using a vacuum calibration die to produce aprofile with a wall thickness from 0.25-0.55 mm and to fit lead waterpipes of 0.5 inch and 0.75 inch (12.5 and 20 mm) internal diameter. Itis also designed to expand radially under pressure while retaining itsstructural and geometrical integrity and be able to recover its shapeeven after the collapse under vacuum. The liner is die drawn duringextrusion while the material is just below the crystallization melttemperature. This enables the liner to be reduced significantly in size(e.g. from 12 to 6-8mm) and also produces significant orientation of thepolymer in the axial direction of extrusion. The form of the reduced diedrawn liner is shown in FIG. 3, which is a cross section of the liner 10showing that the pleats are drawn in-together until their inner surfacesabut. This figure is not to the same scale as FIGS. 1 and 2 and theshrunken liner of FIG. 3 is of much lesser diameter than the liner 10 ofFIG. 1.

When installing the lining, the pipe 11 is thoroughly cleaned by asuitable cleaning method, for example by pumping clean water through thepipe by means of a portable water container fitted with a pressurizedpump attachment. This method has been shown to be useful in washing outdeposits such as oxides which can accumulate in the lead pipe, from theiron water mains. The water also acts as a suitable lubricant forinsertion of the liner; other methods of cleaning such as blowingcleaning sand through the pipeline, or by use of cleaning rods withappropriate attachments may be used. Access is gained to the pipe by wayof a stop cock or chamber boundary box. As shown in FIG. 6, a pig maythen be blown through the pipe 11 with a line attached to be used as aleader for pulling the liner 10 through the pipe for up to 30 meters ormore. Alternatively, a flexible rod may be attached to the liner formoving the liner into the pipe, as shown in FIG. 7. When the liner is inplace, the pipe is reconnected. Pressure of water in the pipe during usewill expand and retain the liner in place, and the liner will preventcontamination of the water by the metal of the pipe. The liner 10 ismade of a selected grade of polyolefin elastomer or plastomer, with awall thickness of between 260-500 or more microns, or sufficient tomaintain the liner's geometric integrity within an existing undergroundhost pipe without collapse.

The use of elastomeric material to form the liner gives substantialadvantages, as the liner can be introduced as a small diameter insertwhich is expanded by application of internal pressure, and has goodresilience and elasticity which are advantageous during introduction ofthe lining to the pipe.

The method and materials described provide a method of rehabilitatingsmall diameter pipes which is free from many of the problems found inthe prior art and provide protection against erosion, corrosion, leadcontamination and deposits of solids (scaling or furring) on the innersurface of the pipe.

No heat activation of the polymer is required, and the liner hasmechanical strength lacking in some proposed film liner's. Also the needto use expensive plant and machinery is significantly reduced.

The liner is able to expand and contract under hydrostatic pressure andis not subject to kinking or twisting even when fed along pipesincorporating bends, and it is able to maintain its original shapearound bends in the flow pipe.

The die drawn liner also has torsional rigidity due to the compacting ofthe pleat due to the die drawing. The liner also has a self supportinggeometrical structure and functions as a hydrostatic valve membrane dueto its elasticity. All these attributes and advantages arise from theuse of the polyolefin elastomer material, the radiated pleatedcross-section and the step of die drawing of the liner as it isextruded.

What is claimed is:
 1. A method of rehabilitating water supply pipes byinserting a tubular liner within a pipe, the method comprising thesteps: positioning a collapsed pleated tube shaped liner at one end ofthe pipe; securing one end of the liner at the end of the pipe;subjecting the liner to movement into the pipe; subjecting the liner toexpansion once inserted in the pipe, the liner expanding to a starshaped multi-lobed cross section, the shape provided by longitudinallyextending radial pleats and ribs; said liner made from a substantiallylinear ethylene inter-polymer elastomer/plastomer.
 2. A method accordingto claim 1, wherein the liner is moved through the pipe by means of aline attached to a messenger pig propelled through the pipe by fluidpressure.
 3. A method according to claim 1, wherein the liner is movedthrough the pipe by means of a flexible rod attached to the liner.
 4. Amethod according to claim 1, wherein the material of the liner has adensity range between 830 and 967 kg/m³.
 5. A method according to claim4, wherein said material comprises 50-95% by weight of ethylene, and5-50% by weight of at least one olefinic co-monomer.
 6. A methodaccording to claim 5, wherein the co-monomer has from 3 to 20 carbonatoms.
 7. A method according to claim 5, wherein the co-monomer is atleast one of: propylene, 1-butene, 1hexene, 4-methyl-1-pentene,1-heptene, or 1-octene.
 8. A method according to claim 1, wherein thematerial of the liner is cross-linked.